Fluid compressor and cooling apparatus therefor



1 B. s. AIKMAN 2,580,341

FLUID COMPRESSOR AND COOLING APPARATUS THEREFOR Filed Sept. 29, 1948 N VEN TOR. e URTON s. A K MAN mg, AT TOR NEY Patented Dec. 25, 1951 UNITEDSTATES ATENT OFFICE FLUID COMPRESSOR- AND COOLING APPARATUS THEREFORApplication September 29, 1948, Serial No. 51,817

4 Claims. (0]. 230-208) This invention relates to air compressors andmore particularly to means for controlling the temperature thereof.

In the operation of air compressors the heat developed by thecompression of air tends to cause carbonization of any oil which mayenter the discharge valve chamber resulting in formation of' a carbondeposit on the walls of said chamber. This reduces dissipation of heatresulting in an even higher temperature in the chamber than otherwisewould occur which tends to warp and crack the discharge valve andassociated elements and render them at least inefiicient in operation ifnot substantially unfit for service. Moreover heat from the dischargevalve chamber is transmitted to other parts of the cylinder head and theadjacent portion of the cylinder wall or walls which tends to burn oiland create carbon deposits thereon.

The principal object of the invention is therefore the provision ofimproved means for so controlling or limiting the temperature of the airin the discharge valve chamber of a compressor as to avoid the abovedifiiculties.

Other objects and advantages will become apparent from the followingmore detailed description of the invention.

In the accompanying drawing, the single figure is a schematic view of amultiple stage air compressor embodying a preferred form of theinvention.

As shown in the drawing, the compressor comprises a cylinder portion lcontaining low and high pressure pistons 2 and 3, respectively, and apressure head 4 secured to the portion I over the pressure ends of thepistons and cooperating therewith to define pressure chambers 5 and 6,

"respectively. The pistons 2 and 3 are adapted to be operated in unisonby rod connections with a common crank shaft (not shown) in the usualmanner. Numeral l designates the piston end of the operating rod for thelow pressure piston 2. 8"de'signates an inlet valveand 9 designates adischarge valve for the low pressure chamber 5, while lli and IIdesignate inlet and discharge valves, respectively, for the highpressure chamvalve chamber [3 is open to the inlet end of an intercooleror heat radiator M the outlet end of which is open to a pipe l5 leadingto a chamber i6, the high pressure inlet valve l0 controlling inlet ofair from chamber It to the high pressure chamber 6. The high pressuredischarge valve II, contained in a discharge valve chamber l'l, controlscommunication between the high pressure chamber 6 and the chamber ll,the latter chamber being open through a pipe l8 to one end of a storagereservoir 19. The opposite end of the reservoir [9 is open through anaftercooler or heat radiator 20 to one end of another storage reservoir2i, the opposite end of which is connected a pipe 22 adapted to conveythe compressed air to a point of use.

The structure so far described is conventional, it being desired topoint out, however, that the intercooler I4 is provided for dissipatingheat from the air compressed thereinto by operation of the low pressurepiston 2 so that relatively cool air will be provided for compression bythe high pressure piston 3 into the reservoir l9, aftercooler 29 andreservoir 2 I, said reservoirs in effect constituting a part of heatradiating means including the aftercooler 20, so that relatively coolair will be delivered to the pipe 22 for use.

According to the invention, an air circulating piston 23 of smallerdiameter than and associated with the low pressure air compressingpiston 2 projects centrally from the pressure head of piston 2 throughthe low pressure chamber 5 into a bore in the pressure head 4 wherein itcooperates with said head to form a chamber 24. An inlet valve 25 isprovided for controlling flow of fluid under pressure from a chamber 26to the chamber 24, while a discharge valve 21 is arranged to controldischarge of air from chamber 26 to the discharge valve chamber l3. Thechamber 25 is open to a passage 28 in the compressor head 2 whichpassage forms a fluid flow connection between the outlet end of theintercooler 14 and pipe is leading to the high pressure chamber 6.

In operation, it will be seen that the air circulating piston 23 willreciprocate with the low pressure air compressing piston 2 and upon theintake stroke of the latter piston will draw relatively cool air fromthe outlet end of the intercooler l4 past the inlet valve 25 intochamber 24, while upon the air compressing stroke of piston 2, thepiston 23 will discharge the relatively cool air from chamber 24 pastdischarge valve 21 into the discharge valve chamber I3 wherein it willmix with the impulse of relatively hot turbulent compressed air beingdelivered past the discharge valve 9 by the low pressure air compressingpiston therefrom to said discharge valve chamber, and

hence substantially no increase in the temperature of the delivered airandth'e size or displace'- ment of the circulating piston 23 is sorelated to the displacement of the air compressing piston 2 that thedesired cooling of the hot compressed air delivered to said dischargevalve chamber results for the purpose above described.

Similarly, a circulating piston 33 of smaller diameter than the highpressure air compressing piston 3 projects from the pressure facethereof into a bore into the pressure head 4 with which it cooperates toform a chamber 29 communicating past an inlet valve 38 and through apipe 3| with pipe 22 at the outlet end of the high pressure heatradiating means including reservoirs IE! and 2| and the aftercooler pipe2 l, and communicating past a discharge valve 32 with the high pressuredischarge valve chamber ll. As will be seen, the

'circulating piston 28 will reciprocate with the high pressure airpiston 3 to draw past the inlet valve 30 relatively cool air from thepipe 22 upon the intake stroke of the latter piston and to dischargethis air past discharge valve 32 and through the discharge valve chamberl7 upon the air compressing stroke of the latter piston, whereby thetemperature of the relatively hot air delivered past the discharge valveH by said latter piston will be reduced by the cool air delivered bypiston 28 to a degree to prevent carbonization of any entrained oil andto also prevent damage to said discharge valve.

By immediately reducing the temperature of the air delivered by the lowand high pressure air com ressin pistons 2 and 3 past the dischargevalves and ii, respectively, to a safe degree as above described, undueheating of the walls of the discharge valve chambers l3 and H andthereby oi the'pressure head I and adjacent portions of the cylinderportion I, as well as of said pistons will also result.

7 Having now described my invention, what I claim as new and desire tosecure by Letters Patent, is:

1. Means for reducing the temperature of ai "in the discharge valvechamber of an air com pressor comprising in combination, a dischargevalve in said chamber, an air compressing piston ior compressingair pastsaid valve into said chamber, air inlet means for said piston, anotherair compressing piston having an intake and, also having a dischargeconnection with said chamber, intake and discharge valves in,respectively, said intake and discharge connections, and heat radiatingmeans connecting said intake to said chamber.

' ing means.

2. In an air compressor having inlet and discharge valve chambers, inletand discharge valves, respectively, in said chambers,'a piston fordrawing air past said inlet valve and discharging it past said dischargevalve into said discharge valve chamber, a second piston secured to andprojecting from the pressure face of the first-named piston, and an aircirculating circuit including said second piston having inlet anddischarge con nections with said discharge valve chamber and alsoincluding heat radiating means.

3. In an air compressor having inlet and discharge valve chambers, inletand discharge valves, respectively, in said chambers, a piston fordrawing air past said inlet valve and discharging it past said dischargevalve into said discharge valve chamber, said compressor having secondinlet and discharge valve chambers and inlet and discharge valves,respectively, mounted therein, a second piston secured to and projectingfrom the pressure face of the first-named piston for drawing air pastsaid second inlet valve and'diScharging it past said second dischargevalve, means opening the two discharge valve chambers to each other, andmeans including heat dissipating means opening the first-named dischargevalve chamber to the second-named inlet valvechamber.

fl. Means for reducing the temperature of the air delivered by thelowand high pressure pistons of a two stage air compressor comprising incombination with said pistons, air inlet means for said low pressurepiston, means including low pressure heat radiating means for connectingthe discharge of said low pressure piston to the intake for said highpressure piston, means including high pressure heat radiating means forconveying fluid under pressure away from said high pressure piston, twoair circulating pistons of smaller diameter than and integral,respectively, with each of said low and high pressure pistons, meanincluding a discharge valve connecting the discharge of each of saidcirculatin" pistons to respectively the discharge of said low and highpressure pistons, and means including inlet valves connecting the inletto the air circulating pistons for'said low and high pistons to,respectively, the outlets of said low and high pressure heat radiat-BURTON S. AIKMAN, REFERENCES CITED The following references are ofrecord in the file of this patent: V

UNITED STATES PATENTS

